Cycloidal motion producing means for printing wheels in high speed printers



July 15, 1969 A. c. TRAB 3,455,237

CYCLOIDAL MOTION PRODUCING MEANS FOR PRINTING WHEELS IN HIGH SPEED PRINTERS Filed Feb. 8, 1968 5 Sheets-Sheet 1 INVENTOR.

ABDULRAHIM CHEIKH TRAB July 15, 1969 A. c. TRAB 3,455,237

CYCLOIDAL MOTION PRODUCING MEANS F PRINTING WHEELS IN HIGH SPEED PRINT Filed Feb. 8, 1968 5 Sheets-Sheet 2 INVENTOR.

ABDULRAHlM CHEIKH' TRAB July 15, 19 A. c. TRAB CY DAL MOTION PRODUCING MEANS FOR PRINTING WHEEL INTERS HIGH SPEED PR Filed Feb. 8, 1968 5 Sheets-Sheet 5 FIG.3

INVENTOR.

ABDULR A HIM CHEIKH TRAB United States Patent Office 3,455,237 Patented July 15, 1969 rm. (:1. B411 47/46; B41j us. Cl. 101-91 Ser. No. 704,077

Feb. 9, 1967,

ABSTRACT OF THE DISCLOSURE In a fixed cylindrical housing, provided at one side with slots open toward a printing platen, several digit wheels are mounted on a continuously rotating shaft coaxial with the housing. Each digit wheel has a hub rigid with the shaft and a surrounding ring with a noncircular inner periphery normally held centered on the shaft axis in spaced relationship with the hub and rotatively entrained in a yieldable manner by a pair of radially outwardly biased pins extending at diametrically opposite locations from the hub; the ring bears two groups of peripherally spaced type faces, each group occupying an arc of somewhat less than 180", and a set of gear teeth engageable with confronting teeth on the inner housing periphery but spaced therefrom in the centered position of the ring. One of the pins, biased more strongly outwardly than the other but normally locked against outward movement by a releasable'detent, acts upon'its release on the inner ring periphery to thrust the ring outwardly with consequent meshing between its teeth and the housing teeth so that the ring-lagging behind the thrust pin-rolls on the housing whereby one of the type faces is pushed outwardly toward the platen after a fraction of a shaft revolution following such engagement; thus, the identity of the operative type face is determined by the angular position of the digit wheel at the instant of release which can be brought about in any of ndiiferent positions (n being the number of type faces in a group, usually by an externally operable selector, Two diametrically opposite ridges of the inner ring periphery cam the released thrust pin back into locking engagement after a printing operation for recentering of the ring and re-entrainment thereof by the hub, whereby the two groups of type faces are alternately utilized during successive printings.

My present invention relates to a high-speed printer as used, for example, in data-processing equipment to record numerical information in a multiplicity of digital columns.

In commonly assigned application Ser. No. 679,037, filed by me jointly with Heinz Ricke on Oct. 19, 1967, there has been disclosed a printer of this general type wherein acylindrical platen performs a cycloidal motion parallel to itself toward a printing roller carrying a plurality of digit wheels. It has also already been proposed Germany, a

10 Claims' described in US. Patent A more particular object of this invention is to provide means in such system for the selection of a desired type face with the aid of a continuously operating planetary-gear drive.

These objects are realized, pursuant to the present invention, by the provision of a generally cylindrical housing surrounding one or more printing wheels each having a hub centered on the housing axis and an annular member surrounding this hub with radial clearance, this annular member being normally centered with reference to the housing and being held on its hub by a coupling mechanism releasably connecting the annular member with the hub for joint rotation. A thrust means mounted on the hub, such as a radially extending pin forming part of the coupling mechanism, is actuatable in selected angular positions of the printing wheel to push its annular member radially outwardly into an off-center position in which a set of fixed gear teeth on the inner housing periphery are engaged by coacting gear teeth on the annular member so that the latter rolls on the inner housing wall toward a lateral slot in that wall confronting an external printing platen. Depending on the hub position in which the thrust means was actuated, any one of a set of type faces on the annular printing member projects outwardly through the slot to contact the platen with a cycloidal motion whereby the character represented by a type face isp'r'inted on an interposed sheet. Upon continuing rotation of the wheel hub about the housing axis, the annular member is restored to its centered position on the hub, advantageously by camming engagement with a formation on that member which returns the thrust means to an inoperative position after the cycloidal motion has carried the selected type face past the printing point at the lateral housing slot.

In accordance with a more specific feature of my invention, the annular member of each digit wheel is a ring with a noncircular inner periphery forming a pair of diametrically opposite recesses and a pair of adjoining ridges also offset by Normally, this ring is held centered on the hub by the aforementioned thrust pin engaging in one of these recesses while a more weakly biased balancing pin is received in the opposite recess. A suitable detent, advantageously an annular clip encircling the hub, locks the thrust pin against radially'outward displacement by its relatively strong biasing force, the ring then rotating in unison with its hub while being disengaged from the gear teeth of the stationary housing. As soon as the detent is deactivated, as by coming into contact with a selectively settable stop mounted on the housing, the thrust pinurges the ring into meshing engagement of its gear teeth with those of the housing whereby the ring begins to roll with reverse rotation on the housing wall so that the recesses heretofore engaged by the two aforementioned inner ridges which eventually returns that pinto a'retracted position wherein the pin is re-engaged by the detent clip As soon as the thrust pin moves off the ridge to confront the adjoining recess (this being the one opposite the recess previously engaged by it), the balancing pinrecenters the ring by a reverse thrust restoring the original starting position with a 180 relative displacement between the ring and the hub. Thus, the outer ring surface should be divided into two segments carrying duplicate sets or groups of type faces, each group extending over an arc of less than 180 so that these groups are separated by blank zones free from type faces which lie in the immediate vicinity of the two internal recesses. I

The above and other features of my invention will become more readily apparent from the following descripa generally cylindrical housing centered on an axis and provided 'with a lateral slot;

a printing wheel in said housing having a hub centered on said axis, said wheel comprising an annular member surrounding said hub with radial clearance, a set of type faces on said member sequentially alignable with said slot and coupling means releasably entraining said member for rotation about said axis with freedom of radial motion of said member between a centered position and an off-center position;

a first set of gear teeth on the inner periphery of said housing;

a second set of gear teeth on said member disengaged from said first set in said centered position but engaging same in said off-center position whereby said member rolls on said inner periphery with reverse rotation relative to said hub;

normally inoperative thrust means on said hub for displacing said member into said off-center position with resulting release from entrainment by said coupling means;

actuating means for said thrust means operable in different angular positions of said hub for selectively aligning any of said type faces with said slot upon said member rolling on said inner periphery, the type face so aligned projecting outwardly through said slot with a cycloidal motion in the off-center position of said member;

a printing platen outside said housing confronting said slot for co-operation with a projecting type face of said member;

restoring means effective upon withdrawal of the pro- 'jecting type face from said slot for returning said member to said centered position with ensuing reentrainment by said coupling means;

and drive means for rotating said hub about said axis.

2. The combination defined in claim 1 wherein said coupling means comprises a radially movable element on said hub bearing upon said member, said thrust means including resilient biasing means urging said element radially outwardly, said hub being provided with detent means normally locking said element against outward movement but disengageable from said element by said actuating means.

3. The combination defined in claim 2 wherein said restoring means comprises a camming formation on said member urging said element inwardly for re-enga'gement by said detent means in a predetermined relative angular position of said hub and said member.

4. The combination defined in claim 3 wherein said member has a noncircular inner peripheral wall with a recess normally engaged by said element, said formation being a ridge extending beyond said recess in the direction of rotating of said hub.

5. The combination defined in claim 4 wherein said element is a first pin projecting radially from said hub in a first direction, said coupling means including a second pin projecting radially outwardly from said hub in a diametrically opposite second direction and resilient balancing means weaker than said biasing means for maintaining said second pin in contact with said member.

6. The combination defined in claim 5 wherein said biasing means includes a pair of springs exerting pressure upon said first pin and said balancing means includes one of said springs exerting pressure upon said second pin, said first pin being provided with a lateral notch and said detent means including an annular clip encircling said hub, the otherof said springs being coupled with said clip for maintaining an edge thereof engaged in said notch.

7. The combination defined in claim 5 wherein said recess is one 'of a diametrically opposite pair of such recesses and said ridge is one of a diametrically opposite pair of such ridges, said pins having tips normally received in said recesses, said type faces being divided into two groups each spread over an arc of less than each type face of one group being identical with a diametrically opposite type face of the other group, said groups being separated by zones free from type faces in the vicinity of said recesses.

8. The combination defined in claim 7 wherein said pins are provided with spring-loaded balls forming the tips thereof and entering said recesses for camming dislodgment therefrom upon incipient relative rotation between said member and said hub.

9. The combination defined in claim 7 wherein said first pin is provided with a lateral notch facing upstream as seen in the direction of hub'rotation and said detent means includes an annular clip encircling said hub in nonlocking relationship with said second pin, said clip having an edge confronting said notch and being spring-loaded in the direction of hub rotation for engagement of said edge in said notch, said clip being provided with a projection and said actuating means comprising an abutment movably mounted on said housing for interposition in the path of said projection to draw edge from said notch.

10. The combination defined in claim 1, further comprising brake means coupled with said actuating means for slowing down the rotation of said hub during rolling motion of said member on said inner periphery.

References Cited UNITED STATES PATENTS 

